1. Field of the Invention
This invention relates to devices for closing the drain hole of a boat.
2. Description of the Prior Art
Many boats have a drain hole located in the transom below the water line. When the boat is moving, the water is forced away from the exterior of the transom and away from the drain hole. The drain may then be opened and water within the boat will exit through the drain hole under the force of gravity. The drain hole may also be opened when the boat is out of the water, allowing water within the boat to escape. These drain holes thus provide a simple and easy means for bailing water out of a boat.
A problem with such drain holes is that they must be tightly sealed when the boat is not moving, since they then lie below the water line. There are a number of boat plugs which have been designed specifically to ensure against leakages. Plugs which are sold with a boat are generally of the compressible stopper type as shown in U.S. Pat. No. 3,812,810 issued to Moeller on May 28, 1974. These plugs include a resilient stopper which, when compressed along its longitudinal axis, expands radially and seals the drain hole. These plugs, however, are still subject to leakage at the sealing point between the stopper and the drain hole and around the movable parts. In addition, the plug may leak due to damage or wear, or the plug may simply be lost or its installation omitted.
Other types of drain plugs have been designed which are less susceptible to loss or damage. These generally employ a ball or other plug which is held within the drain hole by some external force such as gravity or spring tension. U.S. Pat. No. 2,990,798 issued to Pribyl on Mar. 14, 1960 discloses a plug which is held by a tension spring. In U.S. Pat. No. 3,188,994, issued to Dawson on Dec. 16, 1963, the spherical plug is held within the drain hole by a magnet. These devices, however, do not operate automatically and can not be used in conjunction with the standard drain plug.
Another type of drain plug is shown in U.S. Pat. No. 2,655,121 issued to Cuneo on Oct. 13, 1953. This plug includes a ball which is affixed to an arm which is hingedly attached to the transom exterior. This device is automatic and can be used with an interior boat plug although its positioning would interfere with a conventional exterior boat plug. This plug, however, has several inherent problems. Being a hinged device it is particularly susceptible to fouling, particularly since it is for use in water. The action of water, salt, and animal or plant growth can easily inhibit the movement of the plug and may prevent the device from sealing the hole sufficiently or from opening automatically. There is the further problem of installing the device so that the ball is positioned within the hole. The limitation of the vertical and horizontal movement of the ball relative the drain hole requires that the ball be accurately positioned to prevent leakage. This restriction favors the use of a short arm to promote accuracy of alignment. Conversely, since the ball is located within the hole by gravity, it is desirable to have the arm as long as possible. This plug thus has the additional disadvantage that either accuracy or positioning force must be sacrificed to some extent. Finally, this plug design is susceptible to misalignment due to wear on the parts, interference by deposits of some type, or by simple physical damage. Under the stresses which occur near this plug, the hinged arm may be deformed. Misalignment resulting from any of the above causes will preclude a tight seal of the hole and will permit water to enter the boat.